1. Field of the Invention
The present invention generally relates to wireless communications and, more particularly, to the creation of an empirical map of wireless coverage which quantifies the quality of wireless coverage over an area and resolves variations of coverage quality over the area to within the geographic accuracy of available location systems, such as the Global Positioning Satellite (GPS) system.
2. Background Description
Coverage areas for communications are defined only approximately by wireless carriers. Carriers do provide geographic maps of predicted coverage areas; however, existing maps do not define the precise degree of the coverage area or the locations of gaps within the advertised area. The imprecision of the existing maps is on the order of miles. Gaps in coverage may be caused by natural landscape features such as low lying valleys or by man made obstructions such as tunnels or tall buildings. Wireless communications providers may provide a disclaimer with their coverage map as an implied acknowledgment of such gaps.
In order to maintain communications for mobile applications, it is necessary that the mobile communications device be located in an area of reliable communications. For example, automobiles when stationary must be located in the reliable area. Today, the user must find such an area by chance or make a choice based upon personal experience. To maintain communications in a vehicle in motion is even more difficult. A moving automobile or truck on a highway will pass in and out of areas where communications are reliable as it moves. Currently, there is no way to predict where the transitions from good to bad communications occur.
The Global Positioning System (GPS) uses a set of twenty-four orbiting satellites to allow ground-based users to determine their locations. Systems for automotive use have dropped in price to the point where they can be purchased for a few hundred to a few thousand dollars. These systems are either built in to the vehicle (e.g., the Cadillac On-Star system) or are portable in a lap top computer (e.g., the Delorme GPS Tripmate system). Such systems, however, are essentially passive, one way systems; that is, they provide the driver with position information based on GPS data.